This application claims the benefit of Korean Application No. 97-76414, filed Dec. 29, 1997, in the Korean Patent Office, the disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a telephony service, and more particularly, to a telephony service system employing a cable network as well as a public switched telephone network (PSTN), and to a telephony service method.
2. Description of the Related Art
A public switched telephone network (PSTN) supplying an audio communication service to a user has been used to supply local calls, long distance calls and international telephony services. However, with the increased use of the Internet, telephony service using the Internet has been developed and is being used. In particular, the Internet telephony service has advantages of low costs, so that the use of service for providing long distance calls and international telephony services is rapidly increasing.
FIG. 1 is a block diagram of a conventional system supplying telephony service using the Internet or an intranet. In the system of FIG. 1, an intranet 100 (LAN/WAN) is connected to the Internet 118, and the intranet 100 and the Internet 118 are connected to PSTNs 104 and 112 through IP gateways 102 and 110. A directory server 108 storing a directory data base of Internet telephone users is connected to the intranet 100 and the Internet 118. Also, a plurality of terminals such as PCs 116, 120, and telephones 106 and 114 are connected to networks 100, 118, 104 and 112. The telephony service supplied from the PSTN is supplied between phone-to-phone, phone-to-PC, PC-to-phone and PC-to-PC using the Internet 118 or intranet 100.
For example, telephony service provided between two telephones 106 and 114 of FIG. 1 is as follows. For the sake of convenience, the telephone 106, the PSTN 104, and the Internet protocol gateway 102 of FIG. 1 can be a transmitting party, and the telephone 114, the PSTN 112 and the IP gateway 110 can be a receiving party. It is assumed that both users of telephones 106 and 114 have an IP (Internet protocol) address.
The transmitting party contacts the IP gateway 102 through the PSTN 104 using the telephone 106. Also, the transmitter inputs a telephone number of a receiver according to an audio response service supplied from the IP gateway 102. In the IP gateway 102, address resolution of the directory server 108 is required using the input telephone number, and thus an IP address corresponding to the telephone number of a receiver is brought. Also, the IP gateway 102 performs call signaling (H.225.0 protocol) through the H.323 protocol, and negotiates through the H.245 protocol to set an audio session with the IP gateway 110. The IP gateway 110 of the receiver is connected to a telephone 114 of the receiver through the PSTN 112 using the telephone number obtained by negotiating with the IP gateway 102 of the transmitter. If a speech path between the two telephones 106 and 114 is set, the IP gateway 102 modulates an audio signal transmitted from the telephone 106 through the PSTN 104 to generate packet data, which is transmitted to the IP gateway 110 through the intranet 100 (LAN/WAN). The IP gateway 110 demodulates the received packet data to generate an audio signal, which is transmitted to the telephone 114 through the PSTN 112.
The telephony service of the PSTNs of FIG. 1 has the following problems though.
First, since much time is required to initialize a call, service is usually delayed. In order to receive the service, 5 to 8 telephone numbers are input to call the IP gateway adjacent to the PSTN through which the call is being initiated, and then 5 to 8 telephone numbers of the receiver must be input according to the demand of the IP gateway. Also, in public service, a PIN number, e.g., 10-digital ID number must be input. Thus, 30 to 60 seconds are required to realize a call. The IP gateway uses a higher protocol, e.g., TCP/IP (transmission control protocol/Internet protocol) or UDP/IP(user datagram protocol/Internet protocol), which may cause delays compared to the PSTN. Also, the Internet bandwidth varies so that additional delays can be generated.
Second, in order to transmit more data per unit time in transmission of an audio signal, the audio signal is compressed, which may further deteriorate the sound quality. Also, the service delay influences the sound quality.
Third, the above-described method of completing a call is complicated, i.e., telephone numbers must be input twice, and a PIN number must be input.
Fourth, two or more PSTNs are required for a call, so that the call charge is expensive. Thus, the call charges using the Internet phone are saved only for long distance and international calls, and charges for local calls are not saved.
To solve the above problems, it is an object of the present invention to provide a telephony service system employing a cable network together with a PSTN to supply low cost telephony service, and to enable intercommunication with a user of the usual PSTN telephony service, and a telephony service method.
Additional objects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Accordingly, to achieve the above and other objects of the present invention, there is provided a telephony service system between first and second cable phones in a cable network having a directory unit, a plurality of network segment units each including a headend unit, and a plurality of routers respectively formed in each network segment unit.
The directory unit stores the IP address corresponding to a telephone number of a first cable phone. The plurality of network segment units each having a headend unit read IP addresses stored in the directory unit based on a received telephone number from a second cable phone, and determine a connection audio session using an Internet protocol from the read IP address to set a call path with the first cable phone. The plurality of routers set the call path between the network segment units.
To further achieve the above and other objects of the present invention, there is provided a telephony service method between first and second cable phones in a cable network, having three steps. The first step is inputting a telephone number of the first cable phone. The second step is checking a directory to determine whether there is an IP address corresponding to the telephone number input in the first step. The third step is setting a peer-to-peer Internet protocol telephony when it is determined in the second step that there is the IP address, to set a call path between the first and second cable networks.
To still further achieve the above and other objects of the present invention, there is provided a telephony service method between a telephone of a PSTN and a cable phone of a cable network, having seven steps. The first step is inputting a telephone number of a receiving party. The second step is determining, through a directory access protocol, whether the telephone number input in the first step is a telephone number of the PSTN. The third step is setting a call path between the cable phone and the telephone of the PSTN through the Internet telephony gateway if it is determined in the second step that the telephone number is for the PSTN. The fourth step is inputting the telephone number of the PSTN to the cable network. The fifth step is setting a call path with an Internet telephony gateway for connecting the PSTN phone to the cable network through a predetermined network. The sixth step is determining whether there is an IP address corresponding to the telephone number input in the fourth step. The seventh step is setting a peer-to-peer IP telephony between the telephone of the PSTN and the cable phone of the cable network if it is determined that there is the IP address in the sixth step.